The present invention relates to miniaturized sounders and in particular to a buzzer for a pocket paging device or the like.
Pocket pagers have gained wide use and acceptance in recent years. Such pages are commonly used by physicians, repair technicians, and others who must remain in contact with a central location. The pager, which corresponds in size roughly to that of a cigarette package, is carried in a pocket or clipped to the clothing of the user. In one common type of paging system, a radio signal at a particular frequency is generated when contact with the user is required. The radio signal serves to trigger an oscillator within the pager which, in turn, drives a buzzer. The user, upon hearing the buzzer, places a telephone call to the central location to receive his message.
Pocket pagers must be small enough to be comfortably carried by the user. In addition, the pager must be large enough to contain the buzzer along with its associated electronics and power supply. It is thus desirable to miniaturize the components of the pager as much as possible. This poses a particular problem with regard to the actual sounder since it must be capable of generating a sound sufficiently loud to insure attracting the user's attention regardless of ambiant noise conditions.
Heretofore, various attempts have been made to produce such miniature sounders or buzzers. In one such attempt, a folded horn is positioned within a tuned cavity. This, however, requires precise tuning of the buzzer components. In our co-pending application Ser. No. 236,001 filed Feb. 19, 1981 for MINIATURE SOUNDER WITH DOUBLE TUNED CAVITY, a sounder is provided which relies on the tuning of cavities within the sounder housing. A problem of these prior art devices is that since the sounder components are tuned to a particular frequency, in the event of a frequency shift the output will deteriorate. This may or may not be desirable depending upon the ultimate use of the sounder. The "Q" of the sounder is a measure of the sensitivity of the sounder to frequency shift. The lower the Q, the less susceptible the sounder output will be to variations in the drive frequency.
In view of the above, it is the principal object of the present invention to provide an improved sounder which is small in volume, capable of producing a relatively loud, audible sound and in which the Q may be controlled to some extent as required for particular usages.
A further object is to provide such a sounder which is compatible with conventional pocket pager drive circuits and power sources.
A still further object is to provide such a sounder which is reliable, efficient and which may be constructed of a small number of components which may be readily assembled.